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Delhi

Welding- A Fabrication Process

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Published in: Mechanical
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DIFFERENT TYPES OF WELDING: 1. OXY-FUEL GAS WELDING. 2. ELECTRIC ARC WELDING. 3. RESISTANCE WELDING. 4. SOLID STATE WELDING. 5. RADIENT ENERGY WELDING.

Raja H / Kolkata

4 years of teaching experience

Qualification: B.E.(Production Engineering)

Teaches: Algebra, Mathematics, Physics, IIT JEE Mains, WBJEE, Mechanical

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  1. coy • PRESENTED BY- RAJA HOSSAIN
  2. DIFFERENT TYPES OF WELDING: 1. OXY-FUEL GAS WELDING. 2. ELECTRIC ARC WELDING. 3. RESISTANCE WELDING. WELDING.
  3. * What is LASER ? LASER: L A ight mplification by Stimulated * What is Light? Electromagnetic Radiation . Carries Energy in the direction of propagation Wave nature: Transverse Wave i.e. Oscillation of electric & mission of Radiation z magnetic fields are transverse to the direction of propagation. FIG. 1 Velocity in vacuum or air, c = 3x108m/s, Frequency = v , Wavelength = X = c/ v In a medium of refractive index n, Light velocity, v = c/n 8 9 x 03 17 18 10 Hz 10 106 10 5 7 Wavelength is about 3 football fields long. 10 11 12 la 14 15 16 10 10 10 10 10 10 10 10 10 1 Wavelength = c/ nv Particle nature: Photon Energy = hv, Photon momentum p = hv/c h= Planck's constant = 6.626x10-34 J-sec. Wavelength about 3 m or 10 feet long. Wavelength about 3 cm or 1 inch long. Wavelengths 400-700 nm Wavelength about 30 x diameter of hydrogen atom FIG. 2
  4. What is Stimulated Process? Light Matter Interaction Simplest Example : An Atom Nucleus (protons & neutrons) and electron shell (electrons) Bohr model of atom Electrons can only have certain values of energy — not all values of energy allowed! Electrons can switch between energy levels by gaining or losing energy Electrons can gain energy by absorbing a little packet of light — photon: Absorption Can lose energy by emitting a photon: Spontaneous Emission Photon Energy E = 4- El = h v Planck constant h = 6.626068 X 10-34 J-S Inside an Atom Nucleus Electron Orbit 02003 HowStuffWotks FIG .3 nucleus FIG. 4
  5. ABSORPTION & SPONTANEOUS EMISSION OF PHOTONS Ir??:arning pl-?ütc•r? is abs?:?rbed by the atam Nu?:leus Eler-tr?:?n Inc?:?ming is by the atam Absorption FlG.5 Entission En:ited level L?:?wesF. o Higher- energy phat?:?r? is emikted Electron Nu?:leus Lawer-energy is emikted FlG.6 Ordinary Source of Light Emits Light by Spontaneous Emission Process
  6. Einstein theorized and proposed that a photon passing near an excited electron of the same energy would cause the approached electron to return to its ground state and in doing so release its photon of light. Two identical photons would now exist. Stimulated Emission Photons Photon Laser Emits Radiation by Stimulated Process FIG. 7
  7. Laser Design: lasing medium fully reflective mirror 90 1. Lasing medium at ground state. 2. Population inversjon. partly reflective mirror atom in ground state e $01tarféqus &niSstOn e 0 0 o emßsiÖn 0 3. Spontaneous emtsston, start of stimulated emission. 4. Stimulated emission building up. excited atom stimulated emission atom O Lasing medium: * Solid: Nd:YAG, Optical Fiber * Liquid: Dye Laser * Gas: He-Ne, C02, Excimer Ar+ ion * Semiconductor Diodes LASER BEAM PROPERTIES: -Coherent -Monochromatic -Low Beam Divergence / Directional : Focusibility -High Brightness -High Power and High Power Density -Tunability laser 5. Coherent light, with all waves lined up in phase. beam @ 2006 Encyclopedia Britannica, Inc. FIG .8
  8. C02 LASER GENERATION: e (Hi K.E.) + + e (Low K E) + C02 + C02* C02* -+ C02 + Laser Photon CONVENTIONAL GAS FLOWB(G C02 LASER OUTCOUPL.ING HOLLOW ELECIRODES MIRROR (partial teE1ecting) ZnSe Cooling Fluid out Radiation out PZT ZnSe ndow Cooling Fluid in co 2 High Voltage Power supply FIG .9 ndow co 2 TOT-AL. iviLRROR A-mperorneter
  9. PULL TRANSMISSION MIRROR MIRROR DISCHAfiG€ RADIATION POWER SUPPLY EXHAUST FORE O PUMP FIG. 10
  10. SEALED TUBE C02 LASERS Brewsler angle window gain region Laser output Output window Power supply Rear mirror FIG. 12 1. Power up to about 200W is available 2. Laser pulses lasting 0.1 - Imsecs. 3. Good beam quality
  11. GUIDE C02 LASERS The small bore allows high pressure operation and provides rapid heat removal; both of which lead to high power output from a compact unit. Waveguide bore region Metal electrodes Laser output Output window RF power supply Rear mirror Insulators (waveguide reflectors) FIG. 13
  12. TEA C02 LASERS It generate short intense pulses and the extraction of high power per unit volume of laser gas. Pre-ionising UV discharges pre.ionising suppty Pulsed power supply Transverse electrodes Rear mirror FIG. 14 Laser output Output window
  13. PRINCIPLE OF LASER WELDING Thermal Energy beam Melting Point boundary Joint S*eed t,yxupd (hq«So Lee Free Surface Melted Zone Weld Zone Flow Direction FIG. 16
  14. OF Mg ?LLOY: experinuental va]ues mm mrn mm 200 FIG.17 5 100 300 500 600 Welding speed (cm/min) FIG.18 800 3.5 kW Welding. speed Íc.m/rnin) FIG.19
  15. PROPERTIES OFWCONEL 716 WELDSBY C02 LASER Defect-free full penetration conditions depending on welding variables. Welding speed (m/min.) Power 10 . Partial penetration O: Full enetration 2.0 3.0 3.5 4.0 SP (spatter) C (crack) P (Porosity O: Partial/full penetration FIG.20
  16. Lasers for Weldidg Applications & their Characteristics Characteristics Wavelength gm Laser power,cw Pulse energy Efficiency % Beam Diverge Beam Transportation Absorption in metals Life, CW Hrs.) Pulsed (Shots) Size of lasers Maintenance intervals Hr Mode of operation C02 Laser 9.6-10.6 Upto 45kW 1-20 J 10-15 1-3 mr Reflecting mirrors Low -2-15% 1000s. —106 Large 1000-2000 cw & Pulsed: ms- sub-us Nd:YAG Laser 1.06 sOW- 2kW I-IOOJ 2-20 Diode pump 1 — 25 mr Optical fibers Moderate -5-30% -200 Life of —106 lamps Moderate 500-1000 cw & Pulsed: ms- Sub-ps Diode Lasers 0.8-1.0 Up to 4kW 20—40 1-200 mr Optical fibers Moderate -5-30% 1000s. Compact 5,000- 10.000 cw & Modulate Excimer Lasers 0.193-0.354 --Avg.1kW 1-10J, 2-3 2 — 6 mr. Optical fibers High 104-107 (one gas fill) Moderate 500-1000 Pulsed 10's ns Fiber Laser 1.06 IOkW 30 1-2 mr. Optical fibers Moderat Compact 5,000- 10.000 cw & Pulsed: ms
  17. APPLICATIONS 1- Aerospace. 2- Defense/militarya 3- Electronics. 4- Research & development. 5- Medical. 6- Sensors & instrumentation. 7- Petrochemical refining. 8- Communications & energy.
  18. N/A

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